If you are a mediocre applicant, I would definately recommend a sub-I, since it will give the program their best assessment of you as a future intern. However, if you are an above average applicant, I think a sub-I can hurt you more than help you. As a sub-I on a general pediatrics service, you can admit almost any problem in any age of a child. The breadth of pathology is overwhelming. It is more difficult to prepare for a general peds sub-I since you cannot focus your reading on a specific set of topics. The NICU is a bit different sinc the pathology is limited and you will likely see the same diseases over and over throughout the month, such as prematuriy, IVH, IDM, HMD, etc. However, as a sub-I you are more critically assessed by the attending and the expectations are higher. So I would only do a subI if you have to based on the quality of your application for residency.
On a subspecialty elective, it is usually less work and more laid back. Expectations are lower. It is easier to prepare since you can focus your reading on a certain organ system, patient population, etc. It is easier to impress them for these reasons. It may not look as good as doing a sub-I to the recruitment committee, but if your application is strong then it doesnt matter. They just want to make sure that you are easy to work with and are hard working.
I did 2 aways on subspecialty services and used them more for me to get a better look at the programs in which I was interested. Ironically, the hospital I liked much less during the away elective, I liked it much more based just on the interview day. My first choice program did not impress me on the interview day but I knew from my away rotation that it was a fantastic place to train. This shows you that the interview day is very superficial. So based on the aways, the hospital that I thought would be 1 or 2 on my list ended up being 4 or 5 since I knew despite the great interview day I had there that it was a pretty crappy place to spend 3 years as a resident.
As far as OHSU goes, the PD at my med school has a daughter who was an average applicant in med school. She did a heme-onc rotation since it was the only elective left and worked her butt off. She ended up matching there, when the PD said she likely wouldnt even have gotten an interview. So work hard, have a good attitude, and things will work out for you. Best of luck!